Spectral imagers, including spectral imagers and the like, are becoming an important tool in remote sensing for military and commercial applications. A simple, robust, high quality imager suitable for virtually any visible and infrared region does not currently exist. There are also applications where spectra of individual and physically displaced samples are required. These applications may include, for example, obtaining simultaneous absorption or fluorescence spectra of large numbers of biological or pharmaceutical samples, as well as the emission spectra of large numbers of stars.
Three typical problems that arise in designing an imaging spectrometer where light passing through an entrance slit is to be diffracted by a grating parallel to the slit are: (1) reducing or eliminating astigmatism over the spectrum on the image plane; (2) removing field curvature from the spectrum focused onto the image plane; and (3) obtaining good spatial resolution of the entrance slit, including reducing or eliminating astigmatism at different field angles from points on the entrance slit.
Although desirable results have been achieved using prior art apparatus and methods, there is room for improvement. For example, prior art devices may be mechanically sensitive, and may have a reduced capacity to obtain spectra from various physically separated spatial regions. Therefore, novel apparatus and methods that at least partially mitigate these effects would be useful.